In recent years, in order to further improve the performance of semiconductor devices, attention has been attracted to the methods for mounting a semiconductor element in a facedown structure on a wiring circuit board such as a mother board or a daughter board where a wiring circuit is formed (a flip-chip mode, a direct-chip mode, or the like). Namely, there arise various problems in view of performance in the conventional mounting methods. For example, when a semiconductor element is mounted on a wiring circuit board in a packaged form wherein contact is made from the element onto a lead frame with a gold wire, there sometimes occur delay of information communication caused by the wiring, information communication error induced by cross talk, and the like.
On the other hand, in the mounting method according to the facedown mode, the surface electrode of the semiconductor element is directly bonded to the wiring circuit board, so that it is possible to thin a semiconductor device and save its weight. However, in such a flip-chip mode, direct-chip mode, or the like, the semiconductor element and wiring circuit board which are different in linear expansion coefficient from each other are directly electrically connected. Thus, the reliability of the connection is an important problem.
For solving such a problem, a method for improving the reliability of the connection has been adopted wherein a liquid thermosetting resin called an underfill material is injected into the space between the semiconductor element and the wiring circuit board and then cured to form a resin cured article and thereby a stress converging to the electrically connected area is diverged to the resin cured article.
However, for injecting the liquid thermosetting resin between the semiconductor element and the wiring circuit board, it is necessary to provide a space for arranging an injection nozzle in the periphery of the mounting position of the semiconductor element. With the progress of miniaturization and thinning of the semiconductor device, it becomes difficult to reserve such a space for arranging the injection nozzle, so that it has been desired to improve the underfill process of the liquid resin.
The invention is achieved in consideration of such a situation and provides an adhesive film for underfill excellent in relaxation effect of the stress generated in the above semiconductor element and the wiring circuit board and in the connecting electrode parts and also excellent in reliability of the electrical connection between the semiconductor element and the wiring circuit board, and a semiconductor device using the same as a sealing resin layer.